GitLab

Summary:
- Boldface the version-selection UX and increase size by three percent.
- Add text to breadcrumbs to indicate version and stability.
- New `breadcrumbs.html` in `_templates` overrides Sphinx version.

I create a new variable in `conf.py`, **version_stable**, which has the version number for the most-recent stable release. I define this variable in the **html_context** dictionary so that it is visible to the templates.

I use this approach because I was not able to find any other way of discerning the current stable release during the build. Note that the `versions.html` file--which identifies the current stable release--appears to be available only in the **gh-pages** branch and so it is not available at build time.

However, this means that someone will need to update `conf.py` whenever the current stable release changes.

Pull Request resolved: https://github.com/pytorch/audio/pull/3167

Reviewed By: mthrok

Differential Revision: D44112224

Pulled By: carljparker

fbshipit-source-id: e76f5cb6734a784d161342964459577aa9b64cac